1. Field of the Invention
This invention relates generally to pistons for internal combustion engines, and methods for manufacturing the pistons.
2. Related Art
Pistons used in internal combustion engines, such as heavy duty diesel pistons, are exposed to extremely high temperatures during operation, especially along the upper crown of the piston. Therefore, to moderate temperatures, the pistons are typically designed with a cooling gallery beneath the upper crown, and cooling oil is sprayed into the cooling gallery as the piston reciprocates along a cylinder bore of the engine. The oil flows along the inner surface of the upper crown and dissipates heat away from the upper crown. However, to control the piston temperature during operation, a high flow of oil must be maintained constantly. In addition, the oil degrades over time due to the high temperatures of the internal combustion engine, and the oil must be changed periodically to maintain engine life. Furthermore, when the cooling gallery temperature exceeds 350° C., the oil tends to burn, referred to as oil coking, and adhere to the surface of the gallery.